1. Field of the Invention
This invention relates to the design of golf balls and other sporting equipment. More particularly, the invention relates to a nickel-titanium fiber for use in the internal structural design of golf balls employing combinations of wound fibers, including a layer of nickel-titanium alloy fiber windings, and plastic layers inside the exterior cover of the golf ball, and for the construction of strings for use in sports racquets.
2. Description of the Related Art
From its beginnings, golf has been influenced by the availability of balls which represent a continuing effort to provide a combination of characteristics aimed at a specific type of golfer. From the earliest constructions available, a conflict has arisen in which the characteristics of a ball which behaves in a way highly desirable for partial shots and putting is different from the characteristics desired by most golfers from a ball used for driving and full iron shots. Specifically, it has been generally believed that a ball which has a soft feel, which can be produced by a lower compression ball, has a desirable characteristic for providing feedback to the golfer for the "touch" shots around the green. A secondary characteristic which is highly desirable for partial and full short iron shots is that a good deal of back spin may be induced into the ball by the descending blow generally used for such shots. The more highly skilled the golfer, the more desirable these characteristics for the short game become. Thus, the more accomplished golfer, one with a lower handicap and the greater skill and ability to utilize the spin of the golf ball to his advantage, wishes to have a ball which can provide a great deal of backspin when hit with the descending blow of a wedge shot around the green. Similarly, the more accomplished golfer is likely to play on very fast greens and the greens which are found on the professional tours are famed for their extreme speed. Under such circumstances, it is highly desirable that the ball provide a soft feel when hit with a putter. As harder balls have become used by handicappers at a somewhat lower skill level than the professionals, the use of putters with inserts has increased as has the availability of some insert wedge designs which allow the production of more spin from a harder ball. There is presently a great deal of interest in providing clubs which make up for any limitation from the ball on the ability to induce spin, especially if it is with the use of a relatively hard ball. The harder ball, however, does have many advantages for the mid-handicapper, and these benefits have accelerated the desire to provide softer feel by means of the face of the club, rather than to attempt to obtain a soft feel from the ball itself. Two factors which have combined to provide a harder ball are an increased desire for distance from the ball with relatively low club head speeds and a desire for increased durability compared to the balata covered balls used by the tour players in the middle of the twentieth century.
The balls which have been used by tour players in the past and are still much favored by the more accomplished golfer are often those of a wound elastic thread construction around a liquid center, with a balata or synthetic or natural rubber surface. Such balls have a very soft feel and the soft cover, and can induce a great deal of spin which can be effectively used by the accomplished golfer. One reason for a trend towards harder golf balls is that they have a more durable cover made of Surlyn or any of a variety of other relatively durable polymers so that the ball can last many times longer than a balata covered round ball. Another benefit to the solid core, Surlyn covered ball is that it is more resistant to damage of all kinds including the possibility of rupture of the internal windings or any other deformation due to hitting a tree or the like, which would make the ball unplayable.
As the technology of golf balls has improved, there now are some balls which have no less than four layers designed for the purpose of influencing the combination of softness, spin and distance available from the ball to a specifically targeted level of player. Moreover, material such as titanium, magnesium and the like have been introduced into the polymers used within the ball in order to improve binding characteristics and energy transfer. However, such construction using these materials involves a very highly divided state of the powder, even to the molecular level, and thus does not represent a layer of metallic material per se. While there have been suggestions of the use of a variety of materials in windings, and many materials, including rubber, polyamide, graphite and the like have actually been used, these materials have not provided all of the desirable benefits desired, but represent improvements in the design of a golf ball for a specific type of golfer.
In one prior art golf ball, a golf ball is wound with a fiber of high tensile strength fibers of at least 250,000 psi strength to create a high hoop stress layer. However, such a construction creates a relatively hard feeling layer to the ball. Accordingly, there is a continued desire to find constructions which are capable of providing new and important characteristics which may be used in the development of a golf ball directed towards specific groups of golfers. The present invention is directed to a specific application of new technology providing those benefits.
A second area of constant need for improvement is in strings for use in the racquet sports. Many different strand materials have been tried, including animal fibers and artificial fibers such as graphite and nylon. There remains, however, a need for new materials and methods of construction for racquet sports strings that exhibit new and desirable characteristics.